Experimental Study of Aerospace-Based Spray Cooling Based on Vertical Surface Orientation

Abstract

Spray cooling is a promising thermal management solution for aerospace applications. The performance of spray cooling in aerospace equipment will be significantly influenced by several parameters. It is proved that the spray cooling system with spray direction perpendicular to the gravity vector, namely, vertical-surface spray cooling system, has excellent heat transfer performance. However, key parameters regarding the vertical-surface spray cooling system have not been in-depth studied, and thus the underlying mechanism is still unrevealed. In this work, a ground spray cooling system was designed and established. The effects of volumetric flow rate, nozzle-to-surface distance, and coolant inlet temperature on the heat transfer characteristics of spray cooling were experimentally investigated. The Sauter mean diameter of droplet was tested and analyzed. The system shows a magnificent heat dissipation capability as high as a heat flux of 300 W/cm2 at a low volumetric flow rate (0.1 L/min). Nozzle-to-surface distance, which has no obvious effect on the two-phase regime, is observed to play a significant role in the single-phase regime. Interestingly, heat transfer coefficient can be enhanced by increasing the coolant inlet temperature while it will not necessarily lower down the surface temperature. Furtherly, experimental dimensionless correlation of Nusselt number for single-phase regime is proposed, demonstrating a higher contribution of liquid properties to the cooling system performance based on vertical surface orientation. This work is expected to provide guidance for the design of the aerospace-based spray cooling systems.

Keywords: Spray cooling, heat transfer characteristics, Vertical surface orientation, aerospace applications